The objective of the proposed research is to analyze and characterize the wear and deterioration of ultra high molecular weight polyethylene in service as components of total joint replacements. Commercially available knee and hip prostheses are run in total joint simulators with programmed load and velocity cycles, in an environment of bovine serum. The results are compared with clinical material and relative implant performance evaluated. All materials are characterized for molecular weight distribution, crystallinity, and other polymer structural and micromorphological parameters, which are then related to the performance of the material in service. Aging, environmental effects, radiation sterilization procedures and other influences on structure and properties are analyzed. BIBLIOGRAPHIC REFERENCES: Ultrahigh Molecular Weight Polyethylene as Used in Articular Prostheses (A Molecular Weight Distribution Study), by A.M. Crugnola, E.L. Radin, R.M. Rose, I.L. Paul, S.R. Simon and M. Berry. Journal of Applied Polymer Science 20, 809-812 (1976). Giant Cell Synovitis Associated with Failed Polyethylene Patellar Replacements, by F.C. Ewald, C.B. Sledge, J.M. Corsan, R.M. Rose and E.L. Radin. Clinical Orthopaedics and Related Research 15, 213-219 (1976).